Throwaway closure for test tube

ABSTRACT

A disposable plastic closure cap for test tubes dimensioned to fit loosely over the exterior of the open end of a test tube, the cap having an annular plug extending down from the top of the cap to fit into the test tube snugly but not airtightly, the plug surface being in the form of two truncated cones having a common base and different conical angles.

United States Patent Williams Feb. 8, 1972 [54] THROWAWAY CLOSURE FOR TEST FOREIGN PATENTS OR APPLICATIONS TUBE 1,025,894 1/1953 France ..220/DlG. 19 [72] Inventor: Robert J. Williams, Dover, Ohio Primary Examiner-George T. Hall [73] Assignee. gag/gr Molded Products Company, Dover, AtwmeY MaX L. Libman [22] Filed: Apr. 6, 1970 [57] ABSTRACT [21] APP!" 25,888 A disposable plastic closure cap for test tubes dimensioned to fit loosely over the exterior of the open end of a test tube, the 52] us. 01.. ..215/41, 215/47, 220/42 c p having an annular P s emndins down from the top of [51] Int. Cl. ..B65d 41/22, 865d 39/00 the cap to fit into the test tube snugly but not airtightly, the [58] Field of Search ..220/42 C, 42 B, 60, DIG. l9; plug surface being in the form of twbtnmcated cones having a 215/4] 47 common base and different conical angles.

[56] References Cited 1 Claims, 4 Drawing Figures UNITED STATES PATENTS 3,164,279 1/1965 Towns ..215/47 '2 s I 8 4 I -14 A l 5 AL PATENTEU FEB 81972 FIG. 3.

FIG.

FIG.

INVENTOR Robert J. Williams ATTORNEY THROWAWAY CLOSURE FOR TEST TUBE The present invention provides a simple, inexpensive plastic cap which protects the contents of a test tube even more effectively than the usual metal caps, and which is so low in cost that it can be thrown away after each use, as each cap costs less than the expensive sterilizing of the metal caps. Due to the high temperature at which they are molded, the caps emerge from the manufacturing process in a completely sterile condition, and with normal precautions remain in this condition until they are used. The design of the cap is such that the cap is properly centered without the use of springs, and provides an effective closure tightly retaining the contents even during shipping of the tube and contents, in a very simple manner.

The specific nature of the invention, as well as other objects and advantages thereof, will clearly appear from a description of a preferred embodiment as shown in the accompanying drawing, in which:

FIG. 1 is a side view of a test tube provided with a cap according to the invention;

FIG. 2 is a bottom view of the cap looking up into its interi- FIG. 3 is a side view of a portion of the test tube and cap partly broken away in diametric section; and

FIG. 4 is an enlarged view similar to FIG. 3 of a portion of the cap showing details of construction.

Referring to the Figures, a test tube 2 is shown in the upright position, although when shipped with contents it may at least temporarily be turned in any position. In order to prevent contamination of the contents by airborne particles such as bacteria or spores, the cap 3 is provided with a cylindrical sidewall 4 and a flat top 6, and of an internal diameter slightly larger than the external diameter of the test tube 2 so that an annular space 7 is provided when the cap is in place and centered. To effectively seal the contents against leakage, even during shipment, the cap is provided with an internal plug portion 8 extending downwardly from the top 6 of the cap and integral therewith. The plug 8 is annular in configuration, both to conserve material and also to provide resilience so that it tightly engages the inside wall of the vial. The plug may be considered as having two sections, the first section 9 having an exterior surface in the form of a truncated right cone increasing outwardly in diameter from its point of attachment to the top at an angle of substantially l, which is sufficiently small to per mit ready extraction of the cap from the mold cavity. A second section It) continues from the maximum transverse diameter of section 9 and has its exterior surface in the form of a cone reversely oriented to the first cone and preferably decreasing at a considerably larger angle than the first cone,

for example in the order of 30 as shown in FIG. 4, so as to facilitate centering of the plug portion with the test tube when the cap is applied.

The rim of the vial with which the cap is intended to be used is provided with a bead 12 of greater width than the thickness of the vial 2 so that on the inside of the via the bead provides an inwardly projecting rim 1241. When the vial is capped, the plug 8 snaps past this rim due to its elasticity, and thereafter presses outwardly at all points against the inner wall of the vial. The inner bead rim 12a thereafter prevents any possibility of the cap falling out, as a fair amount of force is required to extract the plug from the vial past this inner rim. The long outer skirt 4 keeps the plug from cocking appreciably and this prevents any possibility of leakage due to this factor.

As can be seen from the above, caps 3 made in accordance with the invention are very inexpensive, and present no particular molding problem, so that they can be produced at less cost than the cost of merely sterilizing the metal caps fonnerly used. They are completely sterile when manufactured, and require only to be packaged under reasonably sterile conditions to be immediately usable when the package is opened without further sterilization.

It will be understood that the invention is not limited to the exact embodiment shown and that various modifications can be made in construction and arrangement within the scope of the invention.

I claim: 1. a. In combination with a cylindrical glass test tube having a smooth cylindrical interior wall, a molded plastic closure for said test tube,

b. said closure having a cylindrical wall portion of slightly larger interior diameter than the external diameter of the test tube, sufficient to provide a loose fit,

c. and a substantially circular flat top portion at right angles to said wall portion and closing one end thereof,

(1. an integral annular internal plug portion projecting downwardly from said top portion and concentric with said top portion and of a size to fit snugly and airtightly within said tube when the closure is applied to the open end thereof, by engagement with said smooth cylindrical wall portion,

e. said plug portion having a first section comprising an external conical wall surface increasing outwardly in diameter at an angle in the order of 10 from the vertical for a short distance from its junction with said top portion, to a maximum transverse diameter, said plug portion having a second section comprising an external conical wall surface decreasing from said maximum diameter to a minimum diameter at an angle in the order of 30 to the vertical to provide a reversely tapering tip portion facilitating entry of the plug portion into a test tube,

. said cylindrical wall portion of the closure being of sufficiently greater axial length than the plug portion to prevent any substantial degree of cocking of the plug portion. 

1. A. In combination with a cylindrical glass test tube having a smooth cylindrical interior wall, a molded plastic closure for said test tube, b. said closure having a cylindrical wall portion of slightly larger interior diameter than the external diameter of the test tube, sufficient to provide a loose fit, c. and a substantially circular flat top portion at right angles to said wall portion and closing one end thereof, d. an integral annular internal plug portion projecting downwardly from said top portion and concentric with said top portion and of a size to fit snugly and airtightly within said tube when the closure is applied to the open end thereof, by engagement with said smooth cylindrical wall portion, e. said plug portion having a first section comprising an external conical wall surface increasing outwardly in diameter at an angle in the order of 10* from the vertical for a short distance from its junction with said top portion, to a maximum transverse diameter, f. said plug portion having a second section comprising an external conical wall surface decreasing from said maximum diameter to a minimum diameter at an angle in the order of 30* to the vertical to provide a reversely tapering tip portion facilitating entry of the plug portion into a test tube, g. said cylindrical wall portion of the closure being of sufficiently greater axial length than the plug portion to prevent any substantial degree of cocking of the plug portion. 